1. Field of the Invention
The invention relates generally to a gas purifying apparatus, and, more specifically, to gas purifying apparatus that trap particulate matter contained in gas.
2. Description of Related Art
Diesel particulate filters (DPF) with porous honeycomb structural bodies, that remove particulate matter (PM) contained in exhaust gas emitted from a diesel engine, a lean-burn engine, or the like have been described, for example, in Japanese Patent Application Publication No. JP-A-06-29545. In such described DPFs, a plurality of opening portions passes through the honeycomb structural body from the upstream end face to the downstream end face. Some opening portions are closed at the respective upstream ends and open at the respective downstream ends. Other opening portions are closed at the respective downstream ends and open at the respective upstream ends. Thus, exhaust gas flowing into the opening portions open at the upstream ends is filtered when passing through the porous partition walls. The exhaust gas that passes through the partition walls flows into and is then discharged from the adjacent opening portions that are open at the downstream ends. While the exhaust gas is passing through the partition walls, the PM contained in the exhaust gas is trapped in the partition walls.
An apparatus that includes a cylindrical peripheral electrode that is open at both the upstream end and the downstream end has been described. Specifically, Japanese Patent Application Publication No. JP-A-2004-19534 describes an apparatus having a single rod-shaped center electrode that extends from a position near the upstream end of the peripheral electrode and that passes through the axis of the peripheral electrode. In this apparatus, the PM contained in the exhaust gas, which is electrically-charged by the center electrode, is adsorbed to the peripheral electrode by the interaction between the electric potential and the electric field produced between the two electrodes. A part of the PM adsorbed to the peripheral electrode is burned, and a plasma state is generated due to a high voltage applied between the two electrodes. Then, the oxidation of PM is promoted.